Angioplasty balloon catheters have been developed to treat a variety of different manifestations of vascular disease within patients' veins and arteries that, when not treated, often lead to increasingly serious health conditions and complications, including ischemia, heart attacks, embolisms, and strokes. An angioplasty balloon catheter is generally inserted, along a previously inserted guide wire, into a patient's blood vessel at a variety of different blood-vessel access points, including the femoral, subclavian, radial, and brachial arteries. The catheter is advanced along the guide wire in order to position the inflatable portion of the angioplasty balloon catheter in or near a target region of the blood vessel. The balloon is then inflated in order to mechanically dilate and displace a blockage, lesion, or other problem within the target region. Currently available angioplasty balloon catheters have fixed shaft lengths. As a result, a treatment provider generally selects a balloon angioplasty catheter of appropriate length in order to access a particular treatment site from a particular access point. However, in many procedures, a vessel is blocked at more than one point. In many cases, the treatment provider therefore needs to employ two or more angioplasty balloon catheters of two or more different lengths in order to reach and ameliorate the two or more blockages from the particular access point. Because angioplasty-balloon-catheter-based procedures involve prior insertion of the guide wire, insertion and removal of multiple, different-length angioplasty balloon catheters may result in a variety of cascading complexities and problems, including a need to remove and reinsert different-length guide wires, complexities associated with maintaining sterile protocols across multiple sub-procedures, increased procedure times, and potential for additional complications arising from additional procedural steps, including risk of vessel damage and unintentional vessel-wall penetration. Designers, developers, and treatment providers therefore continue to seek new and improved treatment equipment and associated methods for treating blood-vessel malformations, constrictions, obstructions, lesions, and blockages.